Twin-Roll Continuous Casting Machine And Twin-Roll Continuous Casting Method

ABSTRACT

When a molten steel ( 106 ) is supplied into a moving mold defined by concave rolls ( 101, 102 ) and side checks ( 103, 104 ), the molten steel ( 106 ) is cooled by the surfaces of the rolls (surfaces except steps) to form solidified shells ( 111, 112 ). Both solidified shells ( 111, 112 ) are pressure bonded, and pulled out as a cast piece ( 113 ). A heat insulator (ceramic coating) has been applied to the circumferential surfaces of steps ( 101   a,    101   b,    102   a,    102   b ) which are opposite end portions of the rolls. Thus, at these portions, heat dissipation does not proceed, and no solidified shells are formed. Hence, clearances are formed between the opposite ends of the solidified shells ( 111, 112 ) and the side checks ( 103, 104 ), and the solidified shells ( 111, 112 ) do not contact the side checks ( 103, 104 ), with the result that the wear of the side checks ( 103, 104 ) is prevented.

TECHNICAL FIELD

This invention relates to a twin-roll continuous casting machine and a twin-roll continuous casting method, which are designed to reduce the wear of side checks markedly and prolong the lives of the side checks.

BACKGROUND ART

A continuous casting machine is a machine for continuously pouring a molten steel, whose smelting has been completed, to produce a cast piece (slab or strip) directly. A continuous casting method using the continuous casting machine is minimal in segregation, and satisfactory in surface quality, in comparison with a conventional ingot making or blooming method, and is thus suitable for producing a cast piece for use as a steel plate.

Continuous casting machines include a twin-roll continuous casting machine using a synchronous twin-roll type mold (moving mold) which moves together with a cast piece.

FIG. 8 shows a general example of a twin-roll continuous casting machine 010. With the twin-roll continuous casting machine 010, a pair of rolls 011 and 012 rotating in opposite directions are disposed parallel at the same height in proximity to each other, and the opposite ends in the axial direction of the rolls 011 and 012 are partitioned by side checks 013 and 014 pressed against the roll end faces. The internal space (melt reservoir) of a moving mold defined by the rolls 011, 012 and the side checks 013, 014 is supplied with a molten steel 016 via a nozzle 015.

When the rolls 011 and 012 rotate in the opposite directions (when they rotate in such a manner as to wrap up the molten steel 016 downward) , the molten steel 016 is cooled by contact with the rolls 011 and 012. As a result, solidified shells are formed on the surfaces of the rolls 011 and 012. Both solidified shells grow in accordance with the rotation of the rolls, are pressure bonded and integrated at a minimum gap portion between the rolls 011 and 012, and taken out as a cast piece 017.

Next, an example of a twin-roll continuous casting machine with the roll shape designed to increase the thickness of the cast piece will be explained using what is shown in Japanese Patent Application Laid-Open No. 1984-118249.

FIG. 9 shows a twin-roll continuous casting machine shown in Japanese Patent Application Laid-Open No. 1984-118249, and FIG. 10 is a view taken along line A-A of FIG. 9.

As shown in FIGS. 9 and 10, the internal space of a moving mold, which is defined by a pair of rolls 10 and 11, side checks 12 and 13 pressed against the end faces of the rolls 10 and 11 and partitioning the roll end face sides, and dams 14 and 15 provided in contact with the rolls 10 and 11, serves as a melt reservoir. The melt reservoir is supplied with a molten steel 16.

Steps 10 a and 10 b, each in the shape of a flange, are formed at opposite end portions of the roll 10. Similarly, steps 11 a and 11 b, each in the shape of a flange, are formed at opposite end portions of the roll 11.

When the rolls 10, 11 rotate, the molten steel 16 is cooled by contact with the surfaces of the rolls 11 and 12 (the surfaces include the surfaces of the steps 10 a, 10 b, 11 a, 11 b) to form solidified shells 17, 18. The solidified shells 17, 18 grow as the rolls rotate. In a minimal gap portion where the gap between the step 10 a and the step 11 a and the gap between the step 10 b and the step 11 b are the smallest, portions of the solidified shell 17 formed on the outer peripheries of the steps 10 a, 10 b, and portions of the solidified shell 18 formed on the outer peripheries of the steps 11 a, 11 b are pressure bonded and integrated by a clamping pressure exerted by the steps 10 a, 10 b and the steps 11 a, 11 b. As a result, opposite end portions of the solidified shell 17 and the solidified shell 18 are pressure bonded and integrated, whereby both solidified shells 17 and 18 are joined together in a sack-sewn shape, as shown in FIG. 10, to form a cast piece 19, with the molten steel 16 remaining in a central portion thereof.

The cast piece 19, formed by the pressure bonding of the solidified shells 17, 18 in a sack-sewn shape in the minimal gap portion with the molten steel 16 remaining in the central portion thereof, is pulled out of the rolls 10, 11, transported, and cooled during transport, whereby the molten steel 16 in the central portion is also solidified.

In the example shown in FIGS. 9 and 10, pressure bonding can be performed at end portions of the solidified shells 17, 18 between the steps 10, 10 b and the steps 11 a, 11 b having gaps narrowed therebetween. Thus, even if the gap between the rolls 10 and 11 is widened, the solidified shells 17 and 18 can be pressure bonded in a sack-sewn shape, and the cast piece 17 pulled out of the rolls 10, 11 is solidified at the peripheral surface thereof, although its central portion remains molten. Since the gap between the rolls 10 and 11 can be widened as above, the thickness of the resulting cast piece 19 can be increased. Since the thickness of the cast piece 19 can thus be increased, the amount of the cast piece produced can be increased, and the production of steel plates with various thicknesses can be achieved.

Patent Document 1: Japanese Patent Application Laid-Open No. 1984-118249

Patent Document 2: Japanese Patent Application Laid-Open No. 2000-246399

Patent Document 3: Japanese Patent Application Laid-Open No. 1997-0295106

Patent Document 4: Japanese Patent Application Laid-Open No. 2001-219247

Patent Document 5: Japanese Patent Application Laid-Open No. 1991-155438

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Even with the twin-roll continuous casting machine shown in FIG. 8, or the twin-roll continuous casting machine shown in FIGS. 9 and 10, however, the solidified shells formed on the surfaces of the rolls contact the side checks during casting. The solidified shells move in accordance with the movement of the rolls, so that the side checks are worn by the moving solidified shells. This posed the problem that the side checks were short-lived. If the wear of the side checks progresses, liquid leakage of the molten steel occurs. Thus, if wear progresses to a certain extent, the side checks need to be replaced. In replacing the side checks, casting has to be discontinued, and productivity lowers. Thus, it is desired to lengthen the lives of the side checks.

FIG. 11 is an enlarged view showing the minimal gap portion as a plan view in the twin-roll continuous casting machine shown in FIG. 8, and shows a state in which the end face of a solidified shell 018 formed on the surface of the roll 011 and the end face of a solidified shell 019 formed on the surface of the roll 012 are wearing the side check 013.

That is, a surface of the side check 013, which is pressed against the drums 011, 012, is flat initially. However, upon wearing by the solidified shells 018, 019, a portion of the side check 013 in contact with end portions of the solidified shells 018, 019 is in a depressed state.

The present invention has been accomplished in the light of the above-described conventional technologies. An object of the invention is to provide a twin-roll continuous casting machine and a twin-roll continuous casting method which can extend the life of the side check.

Means for Solving the Problems

A feature of the present invention for solving the above problems is a twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and

characterized in that a heat insulator is applied to portions of peripheral surfaces of the rolls which are on opposite end sides with respect to a roll axis direction and which make a circle in a circumferential direction.

The twin-roll continuous casting machine is also characterized by performing continuous casting using this device.

Another feature of the present invention is a twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and

comprising a vaporizing material imparting device for imparting a vaporizing material to portions of peripheral surfaces of the rolls which are on opposite end sides with respect to a roll axis direction and which make a circle in a circumferential direction.

The twin-roll continuous casting machine is also characterized by performing continuous casting using this device.

Another feature of the present invention is a twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and

in which each of the rolls has opposite ends, along a roll axis direction, of a larger diameter than a diameter of a middle portion of each of the rolls, and has steps at the opposite ends in the roll axis direction, and

characterized in that a heat insulator is applied to circumferential surfaces of the steps of the rolls.

The twin-roll continuous casting machine is also characterized by performing continuous casting using this device.

Another feature of the present invention is a twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and

in which each of the rolls has opposite ends, along a roll axis direction, of a larger diameter than a diameter of a middle portion of each of the rolls, and has steps at the opposite ends in the roll axis direction, and

comprising a vaporizing material imparting device for imparting a vaporizing material to circumferential surfaces of the steps of the rolls.

The twin-roll continuous casting machine is also characterized by performing continuous casting using this device.

Another feature of the present invention is characterized in that the heat insulator is a ceramic coating or a metallic or composite material.

Effects of the Invention

In the present invention, the heat insulator is applied to the portions which are on the opposite end sides with respect to the roll axis direction and which make a circle in the circumferential direction (in the concave rolls, the circumferential surfaces of the steps) In these portions, therefore, heat dissipation does not proceed, and no solidified shells are formed. Thus, clearances are formed between the end faces of the solidified shells and the side checks, and the side checks are not worn by the solidified shells, so that the lives of the side checks are lengthened.

In the present invention, moreover, the vaporizing material is imparted by the vaporizing material imparting device to the portions of the peripheral surfaces of the rolls which are on the opposite end sides with respect to the roll axis direction and which make a circle in the circumferential direction (in the concave rolls, the circumferential surfaces of the steps). Therefore, when these portions enter the molten steel, bubbles are generated by the vaporizing material. As a result, heat dissipation does not proceed at these portions, and no solidified shells are formed. Thus, clearances are formed between the end faces of the solidified shells and the side checks, and the side checks are not worn by the solidified shells, so that the lives of the side checks are lengthened.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) Explanation drawings of various examples of concave rolls.

FIG. 1( b) Explanation drawings of various examples of concave rolls.

FIG. 1( c) Explanation drawings of various examples of concave rolls.

FIG. 2 A front view showing a twin-roll continuous casting machine according to Embodiment 1 of the present invention.

FIG. 3 A view taken along line B-B of FIG. 2.

FIG. 4 A plan view showing a twin-roll continuous casting machine according to Embodiment 2 of the present invention.

FIG. 5 A front view showing a twin-roll continuous casting machine according to Embodiment 3 of the present invention.

FIG. 6 A plan view showing the twin-roll continuous casting machine according to Embodiment 3 of the present invention.

FIG. 7 A plan view showing a twin-roll continuous casting machine according to Embodiment 4 of the present invention.

FIG. 8 A configurational drawing showing a conventional twin-roll continuous casting machine.

FIG. 9 A configurational drawing showing a conventional twin-roll continuous casting machine.

FIG. 10 A view taken along line A-A of FIG. 9.

FIG. 11 An explanation drawing showing the worn state of a side check.

DESCRIPTION OF THE REFERENCE NUMERALS

-   100, 100A, 100-1, 100A-1 Twin-roll continuous casting machine -   101, 102 Concave roll -   101 a, 101 b, 102 a, 102 b Step -   101A, 102A Roll -   103, 104 Side check -   105 Nozzle -   106 Molten steel -   111, 112 Solidified shell -   113 Cast piece -   120, 121, 122, 123, 120A, 121A, 122A, 123A Vaporizing material     imparting device

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described in detail based on the accompanying drawings.

The term “concave roll”, as used in the Embodiments of the present invention, is described first of all. The “concave roll” refers to “a roll in which the diameters of the opposite ends along the axial direction of the roll are larger than the diameter of a middle portion of the roll”.

For example, the “concave rolls” include rolls of various shapes, such as a roll R having steps D at the opposite ends of the roll as shown in FIG. 1( a), a roll R fanning out in a taper form and then having steps D at the opposite ends of the roll as shown in FIG. 1( b), and a roll R in the shape of an hourglass whose diameter progressively decreases toward the center in the axial direction.

If such a concave roll is used at least as one of the rolls, the solidified shells can be pressure bonded in a sack-sewn shape, and a cast piece produced by casting can be thickened.

Embodiment 1

A twin-roll continuous casting machine according to Embodiment 1 of the present invention will be described with reference to FIG. 2 and FIG. 3 which is a view taken on line B-B of FIG. 2.

With a twin-roll continuous casting machine 100 according to Embodiment 1, a pair of concave rolls 101 and 102 rotating in opposite directions are disposed parallel at the same height in proximity to each other, and the opposite ends in the axial direction of the concave rolls 101 and 102 are partitioned by side checks 103 and 104 pressed against the roll end faces. The internal space (melt reservoir) of a moving mold defined by the concave rolls 101, 102 and the side checks 103, 104 is supplied with a molten steel 106 via a nozzle 105.

The concave roll 101 fans out in a taper form and then has steps 101 a, 101 b at the opposite ends of the roll. The concave roll 102 fans out in a taper form and then has steps 102 a, 102 b at the opposite ends of the roll.

Moreover, the arrangement of the concave rolls 101, 102 is set such that the step 101 a and the step 102 a contact, and the step 101 b and the step 102 b contact, in a minimal gap portion.

A heat insulator is applied to circumferential surfaces of the steps 101 a, 101 b, 102 a, 102 b (namely, in the peripheral surfaces of the concave rolls 101, 102, portions which are on opposite end sides with respect to the roll axis direction (roll width direction) and which make a circle in the circumferential direction) (in FIG. 3, the portions given the heat insulator are hatched). Concretely, a ceramic coating is provided by thermally spraying a porous ceramic.

As described above, the application of the heat insulator to the circumferential surfaces of the steps 101 a, 101 b, 102 a, 102 b constitutes a special technical characteristic of the present invention.

A concrete method of applying the heat insulator may be not only coating, but also fitting of a ring-shaped heat insulator, and formation of the rolls such that the material for the rolls is a heat insulator only at those portions.

Also, the coating of the heat insulator may be performed, as appropriate, during pouring.

When the concave rolls 101 and 102 rotate in the opposite directions, the molten steel 106 is cooled by contact with the surfaces of the concave rolls 101 and 102 (these surfaces do not include the surfaces of the steps 101 a, 101 b, 102 a, 102 b) . As a result, solidified shells 111, 112 are formed. The solidified shells 111, 112 grow in accordance with the rotation of the rolls. In the minimal gap portion where the gap between the concave roll 101 and the concave roll 102 is the smallest, end portions of the solidified shell 111 and end portions of the solidified shell 112 are pressure bonded and integrated. At this time, opposite end portions of the solidified shell 111 and the solidified shell 112 are pressure bonded and integrated, whereby both solidified shells 111 and 112 are joined together in a sack-sewn shape, as shown in FIG. 3, to form a cast piece 113, with the molten steel 106 remaining in the central portion thereof.

The cast piece 113, formed by the pressure bonding of the solidified shells 111, 112 in a sack-sewn shape in the minimal gap portion with the molten steel 106 remaining in the central portion thereof, is pulled out of the concave rolls 101, 102, transported, and cooled during transport, whereby the molten steel 106 in the central portion is also solidified.

During the above-described casting, heat dissipation is promoted at portions of the surfaces of the concave rolls 101, 102 which are other than the surfaces of the steps 101 a, 101 b, 102 a, 102 b. Thus, at these portions, the molten steel 106 supplied to the internal space of the moving mold (i.e., melt reservoir) becomes the solidified shells 111, 112. However, the heat insulator has been applied to the surfaces of the steps 101 a, 101 b, 102 a, 102 b, so that heat dissipation does not proceed at the surfaces of the steps, and no solidified shells are formed at the surfaces of the steps.

As described above, no solidified shells are formed at the surfaces of the steps 101 a, 101 b, 102 a, 102 b. In other words, no solidified shells are formed at portions on the opposite end sides, with respect to the roll axis direction, of the peripheral surfaces of the concave rolls 101, 102. As a result, clearances are formed between the solidified shells 111, 112 and the side checks 103, 104, and the solidified shells 111, 112 do not contact the side checks 103, 104, as shown in FIG. 3. Thus, the disadvantage that the side checks 103, 104 are worn by contact with the solidified shells 111, 112 does not arise, so that the lives of the side checks 103, 104 are lengthened.

Since the lives of the side checks 103, 104 are extended, the productivity of casting is increased.

Furthermore, the concave rolls 101, 102 are disposed such that the step 101 a and the step 102 a contact, and the step 101 b and the step 102 b contact. This brings the advantage that the gap between the concave roll 101 and the concave roll 102 can be kept constant with high accuracy.

Embodiment 2

Next, a twin-roll continuous casting machine 100-1 according to Embodiment 2 of the present invention will be explained with reference to FIG. 4. The same portions as those in Embodiment 1 will be assigned the same numerals as those in Embodiment 1, and different portions will be mainly explained, with duplicate explanations being omitted.

In Embodiment 1, the heat insulator is applied to the circumferential surfaces of the steps 101 a, 101 b, 102 a, 102 b, whereas in Embodiment 2, no heat insulator is applied to the circumferential surfaces of the steps 101 a, 101 b, 102 a, 102 b.

Instead, vaporizing material imparting devices 120, 121, 122, 123 for coating a gelled vaporizing material onto the circumferential surfaces of the steps 101 a, 101 b, 102 a, 102 b are provided in Embodiment 2.

A silicone or grease, for example, is used as the vaporizing material. Such a vaporizing material generates a gas when heated by the molten steel 106. This gas creates gaps between the circumferential surfaces of the steps 101 a, 101 b, 102 a, 102 b and the molten steel 106, inhibiting the formation of solidified shells on the circumferential surfaces of the steps. Since this vaporizing material is in a gelled form, the vaporizing material, when coated onto the circumferential surfaces of the steps, does not flow out to other portions. In FIG. 4, the portions coated with the vaporizing material are hatched.

The positions of arrangement of the vaporizing material imparting devices 120, 121, 122, 123 may be positions where neither the molten steel 106 nor the cast piece 113 is present and these vaporizing material imparting devices can contact the circumferential surfaces of the steps 101 a, 101 b, 102 a, 102 b.

The vaporizing material imparting devices are not limited to the above-mentioned coating type devices, but may be of the spraying type.

The features of the other portions may be the same as those in Embodiment 1.

During casting, heat dissipation is promoted at portions of the surfaces of the concave rolls 101, 102 which are other than the surfaces of the steps 101 a, 101 b, 102 a, 102 b. Thus, at these portions, the molten steel 106 supplied to the internal space of the moving mold (i.e., melt reservoir) becomes the solidified shells 111, 112. However, at the surfaces of the steps 101 a, 101 b, 102 a, 102 b, the vaporizing material is vaporized to generate bubbles, so that heat dissipation does not proceed at the surfaces of the steps, and no solidified shells are formed at the surfaces of the steps.

As described above, no solidified shells are formed at the surfaces of the steps 101 a, 101 b, 102 a, 102 b. In other words, no solidified shells are formed at portions on the opposite end sides, with respect to the roll axis direction, of the peripheral surfaces of the concave rolls 101, 102. As a result, clearances are formed between the solidified shells 111, 112 and the side checks 103, 104, and the solidified shells 111, 112 do not contact the side checks 103, 104, as shown in FIG. 4. Thus, the disadvantage that the side checks 103, 104 are worn by contact with the solidified shells 111, 112 does not arise, so that the lives of the side checks 103, 104 are lengthened.

Since the lives of the side checks 103, 104 are extended, the productivity of casting is increased.

A combination of Embodiment 1 and Embodiment 2 would produce the same effects as described above. Other types of concave rolls (see FIGS. 1( a) to 1(c)) can be used in Embodiment 1 and Embodiment 2.

Embodiment 3

Next, a twin-roll continuous casting machine 100A according to Embodiment 3 of the present invention will be explained with reference to FIG. 5 and FIG. 6 which is a view taken on line C-C of FIG. 5. The same portions as those in Embodiment 1 will be assigned the same numerals as those in Embodiment 1, and different portions will be mainly explained, with duplicate explanations being omitted.

In the twin-roll continuous casting machine 100A according to Embodiment 3, rolls 101A, 102A of the flat type (namely, cylindrical rolls having no steps) are used as the rolls.

In Embodiment 3, a heat insulator is applied to portions of the peripheral surfaces of the rolls 101A, 102A which are on opposite end sides with respect to the roll axis direction and which make a circle in the circumferential direction (in FIG. 6, the portions given the heat insulator are hatched) . Concretely, a ceramic coating is provided by thermally spraying a porous ceramic.

A concrete method of applying the heat insulator may be not only coating, but also fitting of a ring-shaped heat insulator, and the formation of the rolls such that the material for the rolls is a heat insulator only at those portions.

Also, the coating of the heat insulator may be performed, as appropriate, during pouring.

When the rolls 101A and 102A rotate in the opposite directions, a molten steel 106 is cooled by contact with the surfaces of the rolls 101A and 102A (these surfaces do not include the surfaces given the heat insulator) As a result, solidified shells 111, 112 are formed. The solidified shells 111, 112 grow in accordance with the rotation of the rolls. In a minimal gap portion where the gap between the roll 101A and the roll 102A is the smallest, the solidified shell 111 and the solidified shell 112 are pressure bonded and integrated.

A cast piece 113, formed by the pressure bonding of the solidified shells 111, 112 in the minimal gap portion, is pulled out of the rolls 101A, 102A, and transported.

During the above-described casting, heat dissipation is promoted at portions of the surfaces of the rolls 101A, 102A which are other than the surfaces given the heat insulator. Thus, at these portions, the molten steel 106 supplied to the internal space of the moving mold (i.e., melt reservoir) becomes the solidified shells 111, 112. However, the heat insulator has been applied to the portions of the peripheral surfaces of the rolls 101A, 102A which are on opposite end sides with respect to the roll axis direction and which make a circle in the circumferential direction. Thus, heat dissipation does not proceed at these portions, and no solidified shells are formed there.

As described above, no solidified shells are formed at the portions of the peripheral surfaces of the rolls 101A, 102A which are on the opposite end sides with respect to the roll axis direction and which make a circle in the circumferential direction. As a result, clearances are formed between the solidified shells 111, 112 and side checks 103, 104, and the solidified shells 111, 112 do not contact the side checks 103, 104, as shown in FIG. 6. Thus, the disadvantage that the side checks 103, 104 are worn by contact with the solidified shells 111, 112 does not arise, so that the lives of the side checks 103, 104 are lengthened.

Since the lives of the side checks 103, 104 are extended, the productivity of casting is increased.

Embodiment 4

Next, a twin-roll continuous casting machine 100A-1 according to Embodiment 4 of the present invention will be explained with reference to FIG. 7. The same portions as those in Embodiment 3 will be assigned the same numerals as those in Embodiment 3, and different portions will be mainly explained, with duplicate explanations being omitted.

In Embodiment 3, the heat insulator is applied to the portions of the peripheral surfaces of the rolls 101A, 102A which are on opposite end sides with respect to the roll axis direction and which make a circle in the circumferential direction. In Embodiment 4, on the other hand, no heat insulator is applied to the peripheral surfaces of the rolls.

Instead, vaporizing material imparting devices 120A, 121A, 122A, 123A for coating a gelled vaporizing material onto the portions of the peripheral surfaces of the rolls 101A, 102A, which are on opposite end sides with respect to the roll axis direction and which make a circle in the circumferential direction, are provided in Embodiment 4.

A silicone or grease, for example, is used as the vaporizing material. Such a vaporizing material generates a gas when heated by a molten steel 106. This gas creates gaps between the molten steel 106 and the portions of the peripheral surfaces of the rolls which are on the opposite end sides, thereby inhibiting the formation of solidified shells at these portions on the opposite end sides of the rolls. Since this vaporizing material is in a gelled form, the vaporizing material, when coated onto the portions on the opposite end sides of the peripheral surfaces of the rolls, does not flow out to other portions. In FIG. 7, the portions coated with the vaporizing material are hatched.

The positions of arrangement of the vaporizing material imparting devices 120A, 121A, 122A, 123A may be positions where neither the molten steel 106 nor the cast piece 113 is present and these vaporizing material imparting devices can contact the portions on the opposite end sides of the peripheral surfaces of the rolls.

The vaporizing material imparting devices are not limited to the above-mentioned coating type devices, but may be of the spraying type.

The features of the other portions maybe the same as those in Embodiment 3.

During casting, heat dissipation is promoted at portions of the surfaces of the rolls 101A, 102A which are other than the portions on the opposite end sides with respect to the roll axis direction. Thus, at these portions, the molten steel 106 supplied to the internal space of the moving mold (i.e., melt reservoir) becomes the solidified shells 111, 112. However, at the portions of the surfaces of the rolls 101A, 102A which are the portions on the opposite end sides with respect to the roll axis direction, the vaporizing material is vaporized to generate bubbles, so that heat dissipation does not proceed at these portions, and no solidified shells are formed at these portions.

As described above, no solidified shells are formed at the portions of the surfaces of the rolls 101A, 102A which are on the opposite end sides with respect to the roll axis direction. As a result, clearances are formed between the solidified shells 111, 112 and side checks 103, 104, and the solidified shells 111, 112 do not contact the side checks 103, 104, as shown in FIG. 7. Thus, the disadvantage that the side checks 103, 104 are worn by contact with the solidified shells 111, 112 does not arise, so that the lives of the side checks 103, 104 are lengthened.

Since the lives of the side checks 103, 104 are extended, the productivity of casting is increased.

A combination of Embodiment 3 and Embodiment 4 would produce the same effects as described above. 

1. A twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and characterized in that a heat insulator is applied to portions of peripheral surfaces of the rolls which are on opposite end sides with respect to a roll axis direction and which make a circle in a circumferential direction.
 2. A twin-roll continuous casting method involving a twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and characterized by performing continuous casting using the rolls having a heat insulator applied to portions of peripheral surfaces of the rolls which are on opposite end sides with respect to a roll axis direction and which make a circle in a circumferential direction.
 3. A twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and comprising a vaporizing material imparting device for imparting a vaporizing material to portions of peripheral surfaces of the rolls which are on opposite end sides with respect to a roll axis direction and which make a circle in a circumferential direction.
 4. A twin-roll continuous casting method involving a twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and characterized by imparting a vaporizing material to portions of peripheral surfaces of the rolls which are on opposite end sides with respect to a roll axis direction and which make a circle in a circumferential direction.
 5. A twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and in which each of the rolls has opposite ends, along a roll axis direction, of a larger diameter than a diameter of a middle portion of each of the rolls, and has steps at the opposite ends in the roll axis direction, and characterized in that a heat insulator is applied to circumferential surfaces of the steps of the rolls.
 6. A twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and in which each of the rolls has opposite ends, along a roll axis direction, of a larger diameter than a diameter of a middle portion of each of the rolls, and has steps at the opposite ends in the roll axis direction, and characterized by performing continuous casting using the rolls having a heat insulator applied to circumferential surfaces of the steps of the rolls.
 7. A twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and in which each of the rolls has opposite ends, along a roll axis direction, of a larger diameter than a diameter of a middle portion of each of the rolls, and has steps at the opposite ends in the roll axis direction, and comprising a vaporizing material imparting device for imparting a vaporizing material to circumferential surfaces of the steps of the rolls.
 8. A twin-roll continuous casting method involving a twin-roll continuous casting machine in which a molten steel is supplied into a moving mold constituted by a pair of rolls rotating in directions opposite to each other, and a pair of side checks pressed against end faces of the rolls, and a cast piece formed by pressure bonding solidified shells solidified on surfaces of the rolls is pulled out of a gap between the rolls, and in which each of the rolls has opposite ends, along a roll axis direction, of a larger diameter than a diameter of a middle portion of each of the rolls, and has steps at the opposite ends in the roll axis direction, and characterized by imparting a vaporizing material to circumferential surfaces of the steps of the rolls.
 9. The twin-roll continuous casting machine according to claim 1 or 5, characterized in that the heat insulator is a ceramic coating or a metallic or composite material.
 10. The twin-roll continuous casting method according to claim 2 or 6, characterized in that the heat insulator is a ceramic coating or a metallic or composite material. 